LITTLE ROCK - A drug wholesaler said Tuesday that it’s investigating whether a lethal injection drug Arkansas bought and had planned to use in a now-halted execution came from a pharmacy that it supplies, a sale that the company says would have violated its contract with the pharmacy.

AmerisourceBergen said it had not distributed midazolam — one of three drugs used in Arkansas’ lethal injection process — to the state Department of Correction. The Pennsylvania-based company declined to name the pharmacy it believed may have sold the drug. Arkansas said it paid $250 in cash in August for enough of the drug to carry out two executions.

“We are investigating the possibility that a pharmacy we service received the product from us and then resold it to the state in violation of our contract,” Gabe Weissman, a spokesman for the company, said in an email. “We buy pharmaceuticals directly from manufacturers, and we adhere to their restrictions on the distribution of their products, including those that prohibit the sale of certain products to correctional facilities. We routinely audit our compliance with manufacturer contracts and policies. In this case, we had no reason to believe that these restrictions had been violated.”

Weissman said the company would investigate what steps it can take to rectify the issue if its contract has been violated, but did not detail what those steps would be.

Documents released last week revealed that Arkansas’ supply of midazolam was made by New York-based Athenex, which said it doesn’t sell drugs if it fears they will be used in executions. The documents were released after the state Supreme Court ruled a 2015 law keeping the source of Arkansas’ execution drugs secret applied to sellers and suppliers of the drug, but not manufacturers.

Athenex declined Tuesday to comment on AmerisourceBergen’s statement. The state Department of Correction declined to comment.

Arkansas had planned to use the drug last week to execute Jack Greene, who was sentenced to death for the 1991 killing of Sidney Burnett, but Green’s execution was halted so justices could consider a lawsuit related to claims Greene is severely mentally ill.

Arkansas put four inmates to death in April, half the number it had intended to execute before its previous supply of midazolam expired April 30. The state acquired more midazolam in August.

Two pharmaceutical companies unsuccessfully tried to block the state from using their drugs in the April executions. A case is pending before the state Supreme Court over a challenge from a medical supply company, which said it was misled by Arkansas prison officials who bought one of its execution drugs.